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Author Topic: Laird Technologies Antenna  (Read 8388 times)
WB6BYU
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Posts: 13026




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« Reply #30 on: May 12, 2011, 10:52:54 AM »

Quote from: AB0RE
...In regards to the performance of a quarter wave, there is a lot of debate about that on the internet.  The "Gold Standard" two meter antenna is the Larsen (Laird) NMO-150 5/8 wave.  The 5/8 wave "in theory" has 3dB gain over the quarter wave which is about a half an S-unit difference.  In actual practice, I've pulled over to the side of the road before and switched between a quarter wave and a 5/8 wave and have not been able to tell the difference.  Additionally, when you are traveling at highway speeds the 5/8 wave, which is longer, will have considerable back-tilt which affects the performance as well...


I have an antenna switch in the car, and have driven down the road switching between a 5/8 wave and a
1/4 wave antenna.  The difference is very slightly in favor of the 5/8 wave whip when signals are marginal,
but if I stop and measure them at any single location either might be better than the other.  I really have to
keep switching back and forth between them as I drive to get a sense of which TENDS to be be a bit better
a little more often.  The practical difference between them is very small, and only observable when signals
are marginal.

The main reason is that the theoretical 3dB gain of the 5/8 wave antenna depends on it being over an
infinite ground plane, and the roof of the average car or van is nowhere close to that on 2m.  You'd need
at least 100' of ground plane in all directions around the antenna.  Without that the 5/8 wave antenna
is at best an end-fed dipole with a 1/8 wave single wire feedline.

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W3LK
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Posts: 5644




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« Reply #31 on: May 12, 2011, 12:21:34 PM »

Yes, this is going to be in all caps to get your attention:

DO NOT USE A PIPE OR CONDUIT PUNCH!!!! USE A CHASSIS PUNCH. THEY ARE NOT THE SAME THING!!!
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W3LK
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Posts: 5644




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« Reply #32 on: May 12, 2011, 12:25:05 PM »


The bolt size I guess is 3/4", thats the sizing on the packaging.

That's the size hole the punch cuts. Measure the bolt, it's 3/8th, if I remember correctly. Maybe it's just me, but I never thought figuring out what size hole to drill was that big a deal when I had the bolt in one hand and a ruler in the other. Smiley
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
KJ4QYM
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Posts: 45




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« Reply #33 on: May 12, 2011, 01:22:06 PM »

Yes, this is going to be in all caps to get your attention:

DO NOT USE A PIPE OR CONDUIT PUNCH!!!! USE A CHASSIS PUNCH. THEY ARE NOT THE SAME THING!!!

Lol I understand, 100% sure the package says 3/4" knockout punch. There was no other types of punches at home depot other than knockout punches, nothing said anything about "pipe" or "conduit" punches, there also wasn't anything that said "Chassis" either but, since the home depot guy said that the kleine products were the same as the Greenlee products I just assumed it was the same thing. I will attach a picture of the product. http://www.homedepot.ca/wcsstore/HomeDepotCanada/images/catalog/15849.53727SEN_4.jpg
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W3LK
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Posts: 5644




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« Reply #34 on: May 12, 2011, 03:03:49 PM »

Yes, this is going to be in all caps to get your attention:

DO NOT USE A PIPE OR CONDUIT PUNCH!!!! USE A CHASSIS PUNCH. THEY ARE NOT THE SAME THING!!!

Lol I understand, 100% sure the package says 3/4" knockout punch. There was no other types of punches at home depot other than knockout punches, nothing said anything about "pipe" or "conduit" punches, there also wasn't anything that said "Chassis" either but, since the home depot guy said that the kleine products were the same as the Greenlee products I just assumed it was the same thing. I will attach a picture of the product. http://www.homedepot.ca/wcsstore/HomeDepotCanada/images/catalog/15849.53727SEN_4.jpg

Measure the diameter of the punch's cutter. If it's not 3/4" then that is NOT what you want. The hole will be the wrong size. Return it and get your money back.
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
K3GM
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Posts: 1767




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« Reply #35 on: May 12, 2011, 03:17:42 PM »

Tyler, here's what Lon is saying.  Some punch sizes are expressed as pipe size.  If you're using a 3/4" pipe, that's the I.d. of the pipe, not the o.d. The punch will be larger than 3/4" to accommodate the wall thickness of the pipe.  You've got the right looking animal.  Just measure across the cup shaped thingy referred to as the die.  If it isn't .750", back it goes!
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K5LXP
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Posts: 4448


WWW

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« Reply #36 on: May 13, 2011, 06:34:48 AM »

After all this dorking around with the punch (once you get the right size) and wrestling with it in the confines of the headliner, slicing up your hands on the roof braces and wiring up there, you will quickly come to the understanding why professional installers use hole saws like the ones Antennex sells with the collar/paint grinder.  Buy one of those along with a spare blade and it's the last one you'll buy in a lifetime.  Makes antenna installations a 15 minute job. 


Mark K5LXP
Albuquerque, NM
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K3GM
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Posts: 1767




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« Reply #37 on: May 13, 2011, 08:42:47 AM »

I have both.  I'll go with the punch whenever possible.
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W3LK
Member

Posts: 5644




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« Reply #38 on: May 13, 2011, 11:58:29 AM »

Probably 95 percent of the holes I have punched have been right over the dome light. Whether you punch or drill/saw, you still have the same conditions getting the coax to the pillar and down.

Pay your money and take your choice.
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
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